Amplifier Compatibility with 2 JBL Woofers

[umar.ghauri176]

Hello guys, as mentioned in previous threads, I`ve purchased 2 12" JBLs GT5 S12 woofers 2

Here the specs:
Each woofer has these specs:
Impedance: 4ohms
Peak power: 1200 watts
RMS power: 300watts.
Voice Coil: Single voice coil
Frequency response: 23Hz - 450Hz
Enclosure: homemade enclosure one box with separate chambers. For image CLICK HERE

Last month I`ve purchased second hand Yamaha amplifier, but cant satisfied with the sound output, actually that amp is home theatre amp, providing 5.1 channel. And I`ve connected 2 woofers in main speakers terminals. I`ve noticed that for music playback, I`ve got bass signals from woofer with vocals as well, but not pure bass.

So I`ve makeup my mind to go for car amp, and for power supply will design power supply according to the requirements of the car amp. or will use computer power supply.

So for car amp want to know that as there are 2 JBL woofers 12 inch, with 300 watts RMS each. so can i go for 4 channel amp or 2 channel amp.

And also which power rating amp can I purchase for these 2 woofers. I mean that on net it says that for power matching consider this formula of:
RMS power + 50% of RMS power means that 300 + 150 = 450 RMS

Which means to purchase amp of 450 watts per channel at 4 ohms.

So which amp is suitable. Is it 4 channel or 2 channel. And what about bridgeable technique. Is it good to have bridgeable car amp ?

Below is website link which provide car amps here in our area, guys please suggest which one best to go for these 2 JBLs. ?

For website link please CLICK HERE

 

[jay32267]

All you need is a two channel amp that actually outputs 300 w rms for each channel.

The problem is...many amplifier manufacturers exagerate the output of their amps by a LOT.....so you need to watch out for this.

 

[americanaudiophile]

To clarify you got a Yamaha AVR just to power the subs (no other speakers).
If you are using it as a power amp, not an AVR, then you would need to connect the subwoofer outputs from another source to stereo inputs of the AVR and then set the AVR for 2.0 operation. I don't think you are doing that since you have vocals coming from the subs.
It won't be as much power as the subs can handle but it will at least be set up correctly.
If you are using the AVR as an AVR and have other speakers connected to it you will need a separate amp connected to the sub out of the receiver.

 

[umar.ghauri176]

To clarify you got a Yamaha AVR just to power the subs (no other speakers).
If you are using it as a power amp, not an AVR, then you would need to connect the subwoofer outputs from another source to stereo inputs of the AVR and then set the AVR for 2.0 operation. I don't think you are doing that since you have vocals coming from the subs.
It won't be as much power as the subs can handle but it will at least be set up correctly.
If you are using the AVR as an AVR and have other speakers connected to it you will need a separate amp connected to the sub out of the receiver.

Hi audiophile how are you.
Actually I`ve got Yamaha avx-700 and at rear of its panel, there`s 2 speaker terminals for main speakers, 2 for rear speakers, 1 for center speaker and a female rca jack for subwoofer.
so I connected 2 woofers in 2 main speaker terminals. That`s why because of connecting woofers in main speakers it gives normal frequency signal to woofers due to which with bass I also hear the vocals and music.
That`s why I want to go for car amp for having pure bass in home. Whats your opinion on that.

So which car amp is suitable. Is it 4 channel or 2 channel. And what about bridgeable technique. Is it good to have bridgeable car amp ?

Below is website link which provide car amps here in our area, kindly suggest which one best to go for these 2 JBLs with 300 RMS each. ?

For woofers website link please CLICK HERE

 

[americanaudiophile]

You do need an separate amp for the subs.
The sub out is mono so It can be a mono amp if it is stable enough and has as much power as you need. When you bridge an amp the minimum impedance is halved so you have to make sure it's stable into 1 ohm in stereo so it will be stable into 2 ohms bridged. A bridged amp will usually produce more than twice the power that it would in stereo which is an advantage when you need a boat load of wattage.
If you go for a car amp you will also need a power supply with enough wattage to operate the amp which adds to the cost. Car woofers are meant to be used in small cabinets so they need more power than a home subwoofer would to get the same result.

 

[umar.ghauri176]

You do need an separate amp for the subs.
The sub out is mono so It can be a mono amp if it is stable enough and has as much power as you need. When you bridge an amp the minimum impedance is halved so you have to make sure it's stable into 1 ohm in stereo so it will be stable into 2 ohms bridged. A bridged amp will usually produce more than twice the power that it would in stereo which is an advantage when you need a boat load of wattage.
If you go for a car amp you will also need a power supply with enough wattage to operate the amp which adds to the cost. Car woofers are meant to be used in small cabinets so they need more power than a home subwoofer would to get the same result.

Hi Audio Guru, yeah you are right for home for car amp im doing RnD for the power supply strong enough to hold the load. Here I`ve found a shop who are making power supply at different rating.

For bridging actually im little confused between half impedance, like you`ve mentioned that
``minimum impedance is halved so you have to make sure it's stable into 1 ohm in stereo so it will be stable into 2 ohms bridged.

Means If I purchase a car amp with 1 ohm per channel, and for 2 channel bridged its 2 ohm, means if i connect each jbl woofer in bridging, so is it be fine ?

Like in this below diagrams:
Normal Wiring 2 ch
Bridge Wiring 4ch
Im I right ? kindly explain bro

 

[americanaudiophile]

If you wire two 4 ohm woofers in parallel they will present 2 ohms to the amp so they amp needs to be stable into 2 ohms.
You need a stereo amp that is stable into 2 ohms in stereo so it will be stable into 4 ohms when bridged into mono.
.

 

[umar.ghauri176]

If you wire two 4 ohm woofers in parallel they will present 2 ohms to the amp so they amp needs to be stable into 2 ohms.
You need a stereo amp that is stable into 2 ohms in stereo so it will be stable into 4 ohms when bridged into mono.
.

Thanks bro now I understood, that amp should be purchased of handling 2 ohm load.
But for bridging I want to know that can I purchase 4 channel amp which can be stable at 2 ohms, and bridge the 2 subs like showing in this IMAGE LINK

Actually here in my area, the car amp outlet deals with 4 channel amps like of Rock-mars.

 

[americanaudiophile]

If your use a four channel amp then it only has to be stable into 4 ohms when bridged since you are using a single speaker on two of the four channels.

 

[umar.ghauri176]

If your use a four channel amp then it only has to be stable into 4 ohms when bridged since you are using a single speaker on two of the four channels.

Hello Dear,

So it means if I use 4 channel amp of rock-mars of 3000 watts. then as one jbl woofer is of 4 ohms so will connect as bridged each woofer to 2 ch. Right ?

 

[americanaudiophile]

You get two channels if you bridge each pair of channels together. You then connect one woofer to each bridged pair.